Skeletal system

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The Skeletal System

The Skeletal System

Parts of the skeletal systemBones (skeleton)JointsCartilagesLigaments (bone to bone) (tendon=bone to muscle)Divided into two divisionsAxial skeleton- skull, spinal columnAppendicular skeleton limbs and girdle

Whats the difference?CartilageTendonsLigamentsToughAttaches bone to muscleAttaches bone to boneFlexibleSturdyElasticAt end of boneNon elasticStabiliseCushionsSize changes depending on muscleMade of many fibresAnchorStrong3Functions of BonesSupport of the bodyProtection of soft organsMovement due to attached skeletal musclesStorage of minerals and fatsBlood cell formation

Bones of the Human BodyThe skeleton has 206 bonesTwo basic types of bone tissueCompact boneHomogeneousSpongy boneSmall needle-like pieces of boneMany open spaces

Classification of bones (Shapes)Long- bones are longer than they are wide (arms, legs)Short- usually square in shape, cube like (wrist, ankle)Flat- flat , curved (skull, Sternum)Irregular- odd shapes (vertebrae, pelvis)

Lets put the bones into the four categoriesLong BonesShort BonesFlat BonesIrregular BonesFemurTarsalsPatellaAtlasHumerusCarpalsCraniumAxisTibiaPelvis (Llium)CervicalRadiusScapulaThoracicUlnaSternumLumbarFibulaRibsSacrumPhalangesCoccyxMeta TarsalsMeta CarpalsClavicle

Types of Bone CellsOsteocytesMature bone cellsOsteoblastsBone-forming cellsOsteoclastsBone-destroying cellsBreak down bone matrix for remodeling and release of calcium

Bone remodeling is a process by both osteoblasts and osteoclasts

Changes in the Human SkeletonIn embryos, the skeleton is primarily hyaline cartilageDuring development, much of this cartilage is replaced by boneCartilage remains in isolated areasBridge of the noseParts of ribsJoints Bone FracturesA break in a boneTypes of bone fracturesClosed (simple) fracture break that does not penetrate the skinOpen (compound) fracture broken bone penetrates through the skin Greenstick- frays, hard to repair, breaks like a green twigBone fractures are treated by reduction and immobilizationRealignment of the boneAxial skeletonAxial skeleton supports and protects organs of head, neck and trunk skull (cranium and facial bones)Hyoid bone (anchors tongue and muscles associated with swallowing)vertebral column (vertebrae and disks)Bony thorax (ribs and sternum)

Appendicular skeletonAppendicular skeleton includes bones of limbs and Bones that anchor them to the axial skeletonPectoral girdle (clavicle, scapula)Upper limbs (arms)Pelvic girdle (sacrum, coccyx)Lower limbs (legs)Articulation- where joints meet, connect, and are formed.

The Skull8 sutured bones in craniumFacial bones: 13 sutured bones 1 mandible

CraniumEncases brainAttachments for musclesSinuses


16Bones of the Skull

Figure 5.1117Paranasal SinusesHollow portions of bones surrounding the nasal cavity

Figure 5.1018The Hyoid BoneThe only bone that does not articulate with another boneServes as a moveable base for the tongue, and other muscle attachments

19The Vertebral ColumnVertebrae separated by intervertebral discs made of cartilageThe spine has a normal S curvatureEach vertebrae is given a name according to its location


21Thoracic cageribsthoracic Vertebraesternumcostal cartilages

True ribs are directly attached to the sternum(first seven pairs)Three false ribs are joined to the 7th ribTwo pairs of floating ribs


23Internal Structure of BoneBone consists of two different types of tissuecompact bone and spongy bone.Another type of tissue called marrow fills the spaces in bonesThere are two types of marrowred and yellow.

Compact BoneCompact bone makes up theouter layer of all bones. Althoughit looks dense and solid, It is fullof holes for nerves and blood vessels.Spongy BoneSpongy bone contains flatand needlelike structuresthat resist stress. Red bonemarrow may fill the openspaces in some bones.Central CavityCentral cavities in long bones usually containyellow bone marrow (fat).Outer MembraneAn outer membranecovers most of a long bone.The inner portion of a membrane contains cells that build up and breakdown bone.

25What are the types and functions of bone cells?Bone (Osseous) Tissue Dense, supportive connective tissueContains specialized cellsProduces solid matrix of calcium salt deposits around collagen fibersCharacteristics of Bone TissueDense matrix, containing:deposits of calcium saltsbone cells (osteocytes) within lacunae organized around blood vesselsCanaliculi: form pathways for blood vesselsexchange nutrients and wastes

Characteristics of Bone TissuePeriosteum: covers outer surfaces of bones consist of:outer fibrous layerinner cellular layer

Matrix MineralsTwo-thirds of the bone matrix is calcium phosphate, Ca3(PO4)2:Reacts with calcium hydroxide, Ca(OH)2 to form crystals of hydroxyapatite, Ca10(PO4)6(OH)2which incorporates other calcium salts and ions

Ca3(PO4)2 + Ca(OH)2 Ca10(PO4)6(OH)2Bone CellsMake up only 2% of bone mass:osteocytesosteoblastsosteoprogenitor cellsosteoclasts

Matrix ProteinsOne-third of the bone matrix is protein fibers (collagen)

OsteocytesLive in lacunae Are between layers (lamellae) of matrixConnect by cytoplasmic extensions through canaliculi in lamellaeDo not divideFunctions To maintain protein and mineral content of matrixTo help repair damaged bone

Osteoblasts & OsteoidImmature bone cells that secrete matrix compounds (osteogenesis)Matrix produced by osteoblasts, but not yet calcified to form boneOsteoblasts surrounded by bone become osteocytesOsteoprogenitor Cells Mesenchymal stem cells that divide to produce osteoblastsAre located in the inner, cellular layer of periosteum (endosteum)Assist in fracture repairOsteoclasts Secrete acids and protein-digesting enzymesGiant, multinucleate cellsDissolve bone matrix and release stored minerals (osteolysis)Are derived from stem cells that produce macrophages

What is the difference between compact bone and spongy bone?Compact Bone

OsteonThe basic unit of mature compact boneOsteocytes are arranged in concentric lamellaeAround a central canal (Haversian canal) containing blood vesselsPerforating CanalsPerpendicular to the central canalCarry blood vessels into bone and marrowCircumferential LamellaeLamellae wrapped around the long boneBinds osteons togetherSpongy BoneDoes not have osteonsThe matrix forms an open network of trabeculaeTrabeculae have no blood vesselsRed MarrowThe space between trabeculae is filled with red bone marrow:has blood vesselsforms red blood cellssupplies nutrients to osteocytes

Yellow MarrowIn some bones, spongy bone holds yellow bone marrow:is yellow because it stores fat

Periosteum and EndosteumCompact bone is covered with membrane:periosteum on the outside endosteum on the insidePeriosteumCovers all bones:except parts enclosed in joint capsulesIt is made up of:an outer, fibrous layerand an inner, cellular layer

Perforating FibersCollagen fibers of the periosteum:connect with:collagen fibers in bonefibers of joint capsules attached tendons ligamentsFunctions of PeriosteumIsolate bone from surrounding tissuesProvide a route for circulatory and nervous supplyParticipate in bone growth and repairEndosteumAn incomplete cellular layer:lines the marrow cavitycovers trabeculae of spongy bonelines central canalsContains: osteoblastsosteoprogenitor cellsosteoclastsIs active in bone growth and repair

What is the difference between intramembranous ossification and endochondral ossification?Bone DevelopmentHuman bones grow until about age 25Osteogenesis:bone formationOssification: the process of replacing other tissues with boneCalcification: The process of depositing calcium salts Occurs during bone ossification and in other tissues

OssificationThe 2 main forms of ossification are:intramembranous ossificationendochondral ossificationIntramembranous OssificationAlso called dermal ossification:occurs in the dermisproduces dermal bones such as the mandible and clavicle

Endochondral OssificationOssifies bones that originate as hyaline cartilageMost bones originate as hyaline cartilageHow does bone form and grow? Blood Supply of Mature Bones3 major sets of blood vessels develop

Blood Vessels of Mature BonesNutrient artery and vein: a single pair of large blood vesselsenter the diaphysis through the nutrient foramenfemur has more than 1 pairMetaphyseal vessels:supply the epiphyseal cartilagewhere bone growth occursPeriosteal vessels provide blood to:superficial osteonssecondary ossification centersThe periosteum also contains:networks of lymphatic vessels sensory nerves

How does the skeletal system remodel and maintain homeostasis, and what are the effects of nutrition, hormones, exercise, and aging on bone?RemodelingThe adult skeleton:maintains itselfreplaces mineral reserves Remodeling:Recycles and renews bone matrix involves osteocytes, osteoblasts, and osteoclasts KEY CONCEPTSBone continually remodels, recycles, and replacesTurnover rate varies If deposition is greater than removal, bones get strongerIf removal is faster than replacement, bones get weakerBone DegenerationBone degenerates quickly Up to 1/3 of bone mass can be lost in a few weeks of inactivityKEY CONCEPTSWhat you dont use, you lose Stresses applied to bones during physical activity are essential to maintain bone strength and massEffects of Hormones and Nutrition on BoneMinerals: A dietary source of calcium and phosphate salts plus small amounts of magnesium, fluoride, iron, and manganese

Calcitriol: The hormone calcitriol, is made in the kidneys and helps absorb calcium and phosphorus from digestive tract its synthesis requires vitamin D3 (cholecalciferol)

Vitamins: Vitamin C is required for collagen synthesis, and stimulates oste